deprecate finders `scope` option

[ro0gr]

Cause it seems to behave in a counter-intuitive way.

A query like:

const node = create({ scope: '.one' });
 
findOne(node, '.two', { scope: '.three' });

generates a selector like .one .three .two.

If a selector like this is really needed, it's possible to do it in a simpler way like:

findOne(node, '.three .two');

I think the rationale for the scope option was to support finder signatures without a string selector argument, like

findOne(node, { scope: '.three .two' });

However, as shown above, in its 3-argument form it looks broken.

Implementation plan

In order to support the 2-argument signature with options, let's implement the new option called selector.
This would be only allowed in the 2-argument signature form:

findOne(node, { selector: '.two' }); 
// => `.one .two`

// together with the `scope` the works exactly like it works today
findOne(node, { selector: '.two', scope: '.three' });  
// => `.one .three .two`

// WRONG: passing 2 selectors should not be possible
findOne(node, '.two', { selector: '.boom' });  
// => Throw!

Then we can deprecate the scope, and remove it at some point.